A Criminal Court verdict in 1998 sentenced Charan Chong-on to 11 years in prison for selling 500 amphetamine tablets while in possession of a firearm after he was arrested by Huay Khwang police. He was also arrested in 1988 by police in Bangkok's Rat Burana district and again in 1993 in Bang Mod district for gambling.

Charan, the man seen wearing sunglasses in television news footage of Monday's clash, and Chaiyasith Lamoh have been charged with the same offences over their alleged assaults on anti-Thaksin supporters at the Central World shopping complex. Three people were injured in the clash.

Meanwhile, a senior police officer accused of ordering the two men to attack anti-Thaksin protestors repeated his denial.

Colonel Ritthirong Thepjanda, a deputy chief of the Metropolitan Police Division 6, said he had submitted a report on the incident to his superior officer and that the internal investigation into the matter was under way.